Most oil and gas wells require stimulation to enhance hydrocarbon flow to make or keep them economically viable. The servicing of oil and gas wells to stimulate production requires the pumping of fluids into the well under high pressure. The fluids are generally corrosive and/or abrasive because they are laden with corrosive acids and/or abrasive proppants, such as sharp sand or sintered bauxite.
In order to protect components that make up the wellhead, such as the valves, tubing hanger, casing hanger, casing head and blowout preventer equipment, wellhead isolation equipment, such as a wellhead isolation tool, a casing saver or a blowout preventer protector is used during well fracturing and well stimulation procedures. The wellhead isolation equipment generally includes a high-pressure mandrel that is inserted through wellhead components to isolate the wellhead components from elevated fluid pressures and from the corrosive/abrasive fluids used in the well treatment to stimulate production. A sealing mechanism, generally referred to as a sealing nipple or a cup tool, connected to a bottom of the high pressure mandrel is used to isolate the wellhead components from high fluid pressures used for well stimulation treatments.
Various sealing mechanisms provided for wellhead isolation equipment are described in prior art patents, such as U.S. Pat. No. 4,023,814, entitled A TREE SAVER PACKER CUP, which issued to Pitts on May 17, 1977; U.S. Pat. No. 4,111,261, entitled A WELLHEAD ISOLATION TOOL, which issued to Oliver on Sep. 5, 1978; U.S. Pat. No. 4,601,494, entitled A NIPPLE INSERT, which issued to McLeod et al. on Jul. 22, 1986; Canadian Patent 1,272,684, entitled A WELLHEAD ISOLATION TOOL NIPPLE, which issued to Sutherland-Wenger on Aug. 14, 1990; U.S. Pat. No. 5,261,487 entitled PACKOFF NIPPLE, which issued to McLeod et al. on Nov. 16, 1993; and Applicant's U.S. Pat. No. 6,918,441 entitled CUP TOOL FOR HIGH PRESSURE MANDREL, which issued Jul. 19, 2005. These sealing mechanisms include an elastomeric cup that radially expands under high fluid pressures to seal against an inside wall of a production tubing or casing.
Elastomeric cups are commonly bonded to a steel ring, sleeve or mandrel. In the most common construction, the elastomeric cup is bonded to a steel ring that slides over a cup tool tube, also referred to as a cup tool mandrel. An O-ring seal carried by the steel ring provides a fluid seal between the elastomeric cup and the cup tool tube.
A cup tool having a unitary elastomeric cup was disclosed in Applicants'co-pending U.S. patent application published on May 4, 2006 under Publication No. 2006-0090904 A1 (McGuire et al.) entitled CUP TOOL, CUP TOOL CUP AND METHOD OF USING THE CUP TOOL which was filed Nov. 2, 2004, the specification of which is incorporated herein by reference.
As shown in FIG. 1, an exemplary embodiment of Applicants' above-referenced prior-art cup tool, designated generally by reference numeral 10, includes a cup tool tube 12, also known as a cup tool mandrel. The cup tool tube 12 includes upper threads 14 for connecting to a high-pressure mandrel (not shown) and bottom threads 16 for connecting to a bullnose 18. The cup tool tube 12 includes an upper annular shoulder 20 disposed beneath the upper threads 14. A gauge ring 22 is retained between a bottom surface of the upper annular shoulder 20 and a top surface of a unitary elastomeric cup 24. The cup can be actuated to provide a high-pressure fluid seal between the cup tool and a surrounding casing or tubing 25. The cup 24 includes a downwardly depending skirt 26 defining an annular cavity 28 between the skirt 26 and the cup tool tube 12. The cup 24 also includes a lip seal 30 that protrudes downwardly and radially inwardly. The lip seal 30 rides against an inner surface of the cup tool tube. The lip seal seals against a tapered region 32 of the cup tool tube 12 when the cup 24 is forced upwardly by fluid pressure to a set position. Pressurization of the annular cavity 28 within the skirt 26 causes the skirt 26 to expand outwardly against the inner surface of the casing or tubing 25 and actuates the cup 24 into the set or sealing position by extruding the upper end of the cup 24 over the gauge ring 22 and into an annular gap 34 between the gauge ring 22 and the casing or tubing 25.